The present invention relates to CAE (Computer Aided Engineering) that optimizes and streamlines design application through numerical analysis simulation using a computer, and more particularly to a technology for automatically generating a mesh for use in numerical analysis simulation.
Before performing numerical analysis simulation, an analysis mesh is generated for use in analysis computation. A tetrahedral or hexahedral mesh is used for a three-dimensional model. For better analysis precision and computation efficiency, a hexahedral mesh should preferably be used. The following describes conventional automatic hexahedral mesh generation methods.
A first conventional method is a mapping method. In this method, the line segments of the shape model of an analysis object are converted to straight line segments parallel with the rectangular coordinate axes, the converted straight line segments are arranged such that they are equivalent to the continuity of the line segments constituting the shape model, a mapping model is generated by dividing and transforming the arranged line segments into a grid, and, with the rectangular grid of the mapping model mapped to the shape model, a hexahedral mesh is generated. This method is disclosed in JP-A-1-311373 and JP-A-2-236677.
A second conventional method is an overlay method. In this method, surface shape data defining the surface shape of an analysis object is input, a fine hexahedral grid parallel with the coordinates axes of the coordinate system in which the analysis object shape is present is generated in the space completely including the analysis object shape, the grid on the inside and/or the surface of the analysis object shape is defined as a mesh, the grid near the surface is modified to represent the shape surface precisely, and a hexahedral mesh is generated. This method is described in U.S. Pat. No. 5,453,934 or in xe2x80x9cBasics and Application of Automatic Mesh Generationxe2x80x9d, pp. 71-74 of document in Third Seminar by the Japan Society for Computational Engineering and Science (Mar. 11, 1998).
The conventional automatic hexahedral mesh generation methods have the problems described below.
When creating a mapping model from a shape model in the first method described above, all line segments of the shape model of an analysis object are converted to straight-line segments parallel with the rectangular coordinate axes, and then the converted line segments are arranged such that they are equivalent to the continuity of the line segments constituting the shape model. However, depending upon the continuity of the line segments constituting the shape model, the mapping model cannot be logically generated. In such a case, the system user must edit the shape before generating a mesh; for example, the user must add line segments to the shape model of an analysis object or delete line segments unnecessary for the generation of the mapping model. For an analysis object that is complex in shape, this preprocessing for mesh generation sometimes requires not only special know-how but also efforts and time.
In the second method, a fine grid parallel with the coordinates axes of the coordinate system, in which the analysis object shape is present, is generated in the space completely including the analysis object shape. Therefore, the number of hexahedral mesh elements increases, resulting in a long analysis calculation. In addition, although the grid elements near the surface are finally modified to represent the shape surface more precisely, highly distorted elements are sometimes generated near the shape surface where, in general, precision is required.
It is an object of the present invention to eliminate the need for shape editing required by the mapping method and to automatically generate a hexahedral mesh ensuring high-precision analysis with fewer elements.
To achieve the above objects, a hexahedral mesh generation device according to the present invention comprises a shape model reader that reads an analysis object shape model, a polygonal patch generator that generates polygonal patches on the surface of the shape model, a mapping model generator that generates a mapping model by modeling after the shape model with the use of a grid from the polygonal patches, and a analysis mesh generator that generates an analysis mesh from the mapping model.